When the Noise gate feature is enabled, the device automatically detects periods of silence during active playback mode and reduces the idle channel power consumption significantly to extend the battery life. This feature is useful for signals playback having long periods of silence, eg voice calls, movie tracks, etc.

The device monitors the input audio signal level against the programmed Noise gate threshold configured by the NG_TH_LVL[2:0] register. When the audio signal falls below the threshold, an internal Hysteresis timer is enabled. If the signal level remains below the configured NG_TH_LVL[2:0] for the entire duration of the NG_HYST_TIMER[1:0], the device enters into the Noise gate mode and reduces the idle channel power consumption. In the Noise gate mode of operation, the high switching blocks like class-D PWM output are turned OFF and outputs are pulled low. The output impedance of class-D can be controlled when the Noise gate mode is active using the CLASSD_HIZ_MODE register. While the Noise gate mode is active, class-D outputs are not switching and the device does not produce any audio output signal. When the device is in Noise gate mode, the NG_STATUS bit is set as high and when the device comes out of noise gate mode, the status bit is set to low.

When the signal level increases above the NG_TH_LVL[1:0], the device automatically wakes up the blocks in low IQ mode and starts playing out the audio input signals. The wake up from Noise gate maintains the signal fidelity by buffering the input signal data during the transition time from noise gate mode to active playback mode. The device does not lose any audio input samples while transitioning from noise gate to active playback.

The transition into noise gate mode and recovery out of noise gate mode is designed to be click and pop-free by following the proper shutdown and power up sequencing.